Risk factors for carbapenem resistant Klebsiella pneumoniae (CRKP) among patients admitted to a liver transplantation unit at a teaching hospital in Brazil

Background: carbapenem resistance among Enterobacteriaceae has been increasing. Risk factors assoicated with this agent are not well understood.

Objective: to determine risk factors for CRKP colonization and infection in patients admitted to a liver transplantation ward (LW) and intensive care unit (LICU).
Methods: a case-control study was performed at a 1000 bed teaching hospital between April 2008 and October 2009. All patients on LICU were screened for CRKP colonization through a rectal swab at admission and at discharge; in LW patients were screened when transferred from other unit. All patients were screened when a new case was identified.
Case patient was colonized or infected by CRKP detected by E-test. Control was defined as a non-colonized patient in the same period. We allocated two controls for each case.
Investigated factors were age, sex, neoplasm, immunosuppression, renal insufficiency, dialysis, diabetes, transplantation, surgery, hospital stay, Charlson, MELD, antimicrobial usage, parenteral nutrition, ventilation, catheter, drains, previous susceptible Klebsiella sp or CRKP or colonization by another carbapenem resistant agent. Categorical and continuous variables were analyzed by chi-square and Mann-Whitney tests respectively. Multivariated analysis was performed by logistic regression. We considered statistically significant p<0.05.
Results: we included 47 cases and 94 controls. Mean age was 50 years, 60% male, 46% transplant recipients. Among cases 43% were infected, 61% bacteremic and 42% died, and presented surgical site infection (44%), pneumonia (17%), urinary infection (17%), bloodstream infection (11%), spontaneous bacterial peritonitis (11%).
Among colonized, there was ertapenem resistance in 100%, imipenem in 7% and meropenem in 12% colonized subjects. In univariate analysis we found significant : dialysis (p=0.02), renal insufficiency (p=0.05), neoplasm (p=0.05), another CR agent (p=0.05). In multivariated analysis renal insufficiency (p=0.01) was identified as risk.
Among infected 100% of CRKP were resistant to Ertapenem, 50% to Meropenem and 25% to Imipenem. Previous colonization by CRKP was found in 78% and average between colonization and infection was 25 days. In univariated analysis risk factors were: dialysis (p=0.004), renal insufficiency (p=0.03) and colonization by CRKP (p=0.001).In multivariated analysis, dialysis (p=0.01) and colonization by CRKP (p=0.01) were identified as risk.  Bacteremia was marginally significant for death (p=0.08)
Conclusions: risk factors for gram negative colonization and infection in this population are not well understood. Carbapenem use has been identified as a risk. Few epidemiologic studies were performed using surveillance culture. In our study, previous use of carbapenems was not significant for CRKP.Renal insufficiency seems to play a role.